1. Field of the Invention
The present invention relates to an automatic speed-change apparatus for a gear transmission.
2. Description of the Prior Art
In the prior art, there has been developed an apparatus in which the mechanism for a manual gear transmission is used as it is and the speed change operation is automated through a hydraulic apparatus by a computer control. However, it requires three cylinders for clutching, shifting and selecting, and a number of solenoid valves to actuate these cylinders, so that it has such problems as complicated structure, large size and high cost.
Also, a speed-change apparatus in which motors are used as actuators to select or shift the gear transmission has been disclosed in JP publication Toku-ko-sho 61-51497, for example. However, this apparatus requires certain numbers of motors depending on the numbers of the select lines, and because of using a plurality of motors or solenoids, it results in a complicated structure and large size apparatus and further in high cost.